US2004/016372 A1 describes a fluid valve comprising an electrical solenoid actuator. When an electric current is passed through the solenoid actuator, it is possible to move a pilot called a ‘push pin’ from a first position to a second position. This pilot, which is not ferromagnetic in US2004/016372A1, is connected to a ferromagnetic armature. A movable valve member is connected to the pilot, and serves to control the flow rate of fluid between the inlet and outlet ducts of the fluid valve. Particularly in paragraph [0015], US2004/016372A1 teaches that the valve member is designed to move in a manner equivalent to that of the pilot.
The valve described in US2004/016372 A1 has a number of drawbacks. For some applications, it is desirable for the valve member to be able to move a long distance or travel over a long path. A long travel path of the valve member enables proportional regulation of larger flow rates. In fact, if one attempts to regulate a large flow rate with a short travel path, sensitivity is lost (the same millimeter of travel would represent a larger flow rate differential). Moreover, if the travel path is not long enough, the valve member might induce unacceptably large charge losses (even when the valve is completely open). At the same time, it is generally desirable to limit charge losses to the valve terminals, so it is essential for the travel path to be suitable for the flow rate that passes through it. The applications for which large travel paths are more beneficial are thus large flow rate proportional regulation applications (more than 1500 L/h, for example).
For the valve of US2004/016372 A1, some long travel paths may become impossible to achieve. On the other hand, with this known system, as the required length of the valve member travel path increases, so the overall mass of the fluid valve also becomes greater. In order to achieve long travel paths, in fact, a large grand valve member and/or a large pilot must be provided. This increases the weight of the fluid valve. On the other hand, if the moving elements (valve member and pilot) are large, then it is generally necessary to provide an actuator solenoid (or coil) that is large enough to be able to move them: A device must be provided that is capable of exerting a substantial force on the pilot. In this case, it often becomes necessary to pass an electric current through the solenoid that is sufficient to generate a magnetic field strong enough to displace the moving elements such as the pilot. However, for certain applications, for example aviation, it is desirable to have a valve of limited size and weight and/or to be able to use a small current in the solenoid.